1. Field of the Invention
The invention relates to a reproduction device for the production of stereoscopic effects in at least a locally limited zone of its observation zone which is located in front of it, with:
a flat display screen, on which stereo images can be shown as vertically divided image strips which are rastered together pairwise, and
a lenticular plate, which is mounted in front of the flat display screen and bears vertically running cylindrical lenses, which are associated each with a respective image strip pair displayed on the flat display screen.
2. Discussion of Relevant Prior Art
Such a reproduction device can already be derived from a large number of publications, since it is suitable for the production of images which are perceptible autostereoscopically, that is, three-dimensionally without additional optical auxiliary means.
The reproduction device known from DE-OS 39 21 061 forms the state of the art from which the invention proceeds; in it, the three-dimensional imaging character of the images produced is attained by a rastering together, in strips on a flat display screen, of two camera signals which are recorded from the object to be imaged in the natural eye spacing, and by a separate supply of the image strips by means of a lenticular plate mourned in front, to the left or right eye of the viewer. An air gap is present between the display screen and the lenticular plate. Means can be provided in such a reproduction device for improving the quality of the locally limited space image reproduction. Correction measures on the lenticular plate itself, such as a change of the lens pitch width or plate thickness, count as such means. For a reproduction device having a surface relief structure which reduces interfering light, it is known from EP-OS 0 493 863, in addition to the said corrective measures, to change the radii of the individual cylindrical lenses.
It is further known from the above-cited DE-OS 39 21 061 to effect an optical image correction by changing horizontally and frontally the relative, plane-parallel position of the lenticular plate with respect to the display screen. A variable air gap is provided for this purpose between the lenticular plate and the display screen. The positional correction takes place in dependence on the eye position of a single viewer, so that an adjustment of the image content for him is possible. The viewer no longer needs to hold his head relatively stiffly. Such image matching can be effected manually, by remote control, or interactively by a corresponding detection of the viewer's eye position, in order to attain a further improvement of comfort (so-called "head tracking process").
For the same problem, a system is also known from EP-A 0 354 851 which has vertically divided image strips which are pairwise rastered together on an active display screen, electronically controlled in order to be displaced by the amount of a respective pixel column when the viewer leaves a zone in which the heretofore stereoscopic effect was perceived by him. In this maimer he also perceives the same image content as before in his new position. This solution, in order to offer the viewer a large freedom of movement in front of the reproduction device, thus stands instead of the mechanical-optical measures according to the previously mentioned DE-A 39 21 061.
The said aspects are also to be gathered, in the nature of general statements for the technological background for such reproduction devices, from a series of other documents. At this point there may be mentioned the articles, "Three-Dimensional in Large Format" (W. Hascher, Funkschau 15/1992, pages 22-26; "A Display for Autoscopic 3D-Television" (H. Isono, M. Yasuda, NHK Lab. Note No. 398, 12/91, compiled by Dr. G. Pollakowski, printed in Fernseh-und Kino-Technik (Television and Cine Technology) 5/1992, Year 46, pages 343-345); "Interactive stereoscopic computer graphic display systems" (N. Storey, J. F. Craine, Conference Papers Vol. 326, Interact '84, First IFIP Conference on "Human-Computer Interaction", Sept. 4-7, 1984, London, pages 382-387) and "Three Dimensional Media Technology" (Proceedings of the 1989 International Conference, Hal Thwaites, published by the 3Dmt Research and Information Center, Montreal, Quebec, Canada).
To achieve as natural as possible a spatial depth effect, the reproduction devices according to the said state of the art strive for a high horizontal image resolution by means of as fine as possible a rastering together, parallel to the lenses, of the two partial images of a stereo photograph. (It is also known, from the said article "Three-Dimensional in Large Format", W. Hascher, Funkschau 15/1992, pages 22-26, to use the signals from four color cameras for 3D representation, but again only two signals are used per viewer. Hence such photographic processes are to be included in the concept of "stereo photographs".) Because of the imaging geometry of the cylindrical lenses to be used for a high depth resolution, relatively narrow zones arise in the whole observation range, with the information for either the left or the right eye of the viewer. The narrow zones lie alternatingly adjacent, and the viewer has to choose his head position so that each of his eyes is associated with the correct narrow zone. Only then can the images be perceived autostereoscopically. If the viewer alters his position such that the image information is supplied to his eyes in an incorrect relationship, he sees pseudoscopically, with a false perception of depth. Sudden jumps in depth occur in the transition into the zones of pseudoscopic vision. However, the pseudoscopic zones are disturbing for the viewer. In order to obtain constantly correct image information, the viewer must hold his head in a very narrowly limited observation zone. Double images arise in the image edge regions by internal and external image crosstalk.